Through recent advances in the personal computer industry, it has become much more feasible to operate highly sophisticated software on these systems. For example, microprocessing speed, random access memory and hard disk storage space have all increased dramatically, among other advances, each of which aid processing. Hard disk storage space once considered ample would likely be inadequate to store some of the more sophisticated and storage consuming programs in use today.
While the storage capabilities of these hard disks have generally increased in storage capacity, their overall dimensions have typically decreased in size which is highly advantageous for use in laptop computers or the like. Part of the reason for these improvements is the technological advancement of read/write heads, servo motor control and servo systems which improves tracking. As a result, the density of the data tracks have substantially increased from about 500 tracks per inch (TPI) to about 3000 TPI which has allowed smaller diameter disks while increasing storage capacity.
Because of this increased track density, however, the importance of rotation trueness of the spindle and disks about a longitudinal axis thereof is magnified. Any wobble, deflection or non-repetitive run-out caused by an imbalanced or offset overall center of gravity from the longitudinal axis can significantly and adversely affect tracking performance. Thus, it is desirable to spin balance the spindle/disks combination in a manner reducing the combined moment of inertia thereof about the longitudinal axis to within an acceptable predetermined tolerance.
Typically, small lead weights of various mass, depending on the particular application, are mounted to a stamped disk mounting clamp employed to fix the disks to the spindle. This clamp includes a circumferentially extending trough formed to receive the weight therein which is situated a fixed distance from the longitudinal axis. An adhesive, as well as the trough walls forming the trough, retains the weight in place during operation once the exact weight and predetermined angle from a known point are determined.
While this balancing technique has been adequate to reduce the combined moment of inertia about the longitudinal axis to within a tolerable level, each application may require a different mass weight since the distance of the trough from the longitudinal axis is fixed. Hence, a plurality of different weights need to be stocked or the weights need to be cut to size for balancing purposes. Moreover, since lead is fairly malleable, these lead weights are easily deformed during installation and/or cutting which in a worse case scenario, alters the positioning of the center of gravity of the weight relative the longitudinal axis of the spindle.
More recently, heat shrink clamps have been employed in the newer disk drives which are unable, due to design, to provide the circumferential troughs to receive the balance weights. Merely mounting the weights, by adhesive, to the planar surface of the clamp has proven problematic due to the small surface area of the adhesive provided under the weight. Hence, there is a chance the weight may dislodge during operation which would not only cause tracking problems but also may damage the electronics and/or mechanisms inside the hard disk drive.